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      • 水稻의 播種樣式과 播種量이 移秧機用 苗素質에 미치는 影響

        金文圭,金聲來,安壽奉 충남대학교 농업과학연구소 1978 農業技術硏究報告 Vol.5 No.2

        In order to get healthy seedling of rice suitable for rice transplanter, the growing characteristics of the seedling grown under different growing days and sowing densities were invesigated and the results obtained were summarized as follows; In the 20 days old seedling, the difference of growing state of seedling and its characteristics between the two types of nursery bed was not found, but for the 30 days old seedling, both of the crop growth rate and the relative growth rate on the band-type nursery bed appeared higher than those on the mat-type nursery bed. And also, the dry weight, the content of cardohydrate and the ratio of dry weight to plant height of the seedling grown on the band-type nursery bed were much higher than those on the mat-type nursery bed, however the amount of difference of seedling characteristics between two types of nursery bed was decreased for 40 days old seedling and leaf number was not increased. The amount of the seedling growth was increased with less density of sowing and for the difference between the higher and the less density, the difference getting bigger with the longer nursery days. The maximum density of sowing was approximately 200cc per nursery case on the band-type nursery bed and 250cc per nursery case on the mat-type nursery bed. It was seemed that the growing uniformity of the seedling grown on the mat-type nursery bed was better than that on the band-type nursery bed, As the coefficient of variation of the plant height and leaf numbers of the seedling grown on the band-type nursery bed was higher than that on the mat-type nursery bed.

      • 흙의 密度와 含水比가 剪斷强度에 미치는 影響

        趙成燮,姜信業,姜乂默,金成完,金聲來 충남대학교 농업과학연구소 1978 農業技術硏究報告 Vol.5 No.1

        It has been known that the shear strength of soil is an important design parameter for the foundation of structures, the retaining walls, the slope failures and so forth. In this study, the shear test was performed by using the direct shear apparatus under various degree of the moisture content and the density of the sample soils. The results of the study were summarized as follows; 1. The shear strength of soil increased with increase in the dry density of soil, and at the same level of density of the sample the shear strength of soil showed large values on a good grading of the sample. 2. The cohesion of the soil varied directly with the dry density of it, however the internal friction angle of soil was not affected by the dry density of the sample. 3. The shear strength of sample varied inversly with the moisture content of it, and this phenomenon was apparent on a good grading of sample. 4. The cohesion of soil showed maximum value when the moisture content of the soil reached optimum level and the internal friction angle decreased with increase in the moisture content of it. These phenomena were very obvious on a good grading sample, SDC-1. 5. The cohesion of the soil decreased with increase in void ratio of the sample, but the internal friction angle of the sample didn't show such tendency.

      • 耕耘實驗을 爲한 人工土壤의 物理的 特性에 關한 硏究

        金基大,許潤根,金滿秀,金聲來 충남대학교 농업과학연구소 1978 農業技術硏究報告 Vol.5 No.2

        For improvement and new design of tillage equipments, indoor test is very useful and more desirable than outdoor because the experiment of ourdoor is very difficult and its cost is expensive. This study was carried out to determine the physical properties of artificial soil suitable for the indoor test with the soil bin manufactured at the workshop of the Dept. of Agricultural Machinery Engineering. The artificial soil being studied was made with very similarity to the natural soil of the experimental plots of Chungnam National University, and it consist of 39.35 percent, by weight of bentonite and 48.10 percent of sand with 12.55 percent of SAE 10W oil. The results are summarized as follows: 1. Bulk density increased with increasing number of rolling, and its relationship could be expressed. y=1.073200+0.07080x-0.002263x^2 where, y=bulk density(g/㎤), x=number of rolling. These results could be explained that the effect of rolling velocity on the bulk density was not singnificant in the range of 4.5∼10.4 cm/sec. 2. The absolute soil hardness depended directly upon number of rolling, and their relationship could be expressed by the equation. y=37.74(0.64+0.17x-0.0054x^2)/(3.36-0.17x-0.0054x^2)^3. where, y=absolute soil hardness(kg/㎤), x=number of rolling. 3. Relationship between the bulk density and absolute soil hardness could be expressed by the equation; y=37.74(2.46 x-2.02)/(6.02-2.46x)^3. where, y=absolute soil hardness, x=bulk density. 4. The cohesion and the angle of internal friction of artificial soil were increased with increasing its bulk density. According to the cohesion and angle of internal friction, at the range of 1.60∼1.75(g/㎤) of bulk density, this artificial soil was similar with sandy loam of 29.5% moisture content of natural soil. 5. Sliding-fricfion coefficient of steel plate on the artificial soil was 0.3∼0.4 and rubber plate on it is 0.64∼0.72. Those values were very similar with those of natural soil being studies by many others.

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